Article ID: 154628 - View products that this article applies to.
This article was previously published under Q154628
If SQL Server is hit with multiple and simultaneous TCP/IP connection requests, such as the case with World Wide Web servers, the requests are quickly rejected by responding with a TCP/IP Reset Frame.
This symptom is difficult to detect. If the client application includes error code handling, the native error code is 10061 (WSAECONNREFUSED) for the Open() function. On the server, Error 17832 - "Unable to read login packet" appears in the SQL Error log.
If you trace this problem with a protocol analyzer, you can see that some of the connection request frames have been replied to with the TCP Reset bit set, which tells the sending station that the frame has been received, but the server does not have the resources to process the connection request.
A Winsock application accepts connections on a port by calling a Listen() function, which has a backlog parameter specifying the maximum length of the pending-connection queue. The Winsock specification defines the maximum Listen() backlog at five and when it exceeds five, TCP/IP issues a reset.
The backlog for SQL Server can be configured to handle a great number of pending connections by modifying the Windows NT Registry. In some cases, the connection reset issue is resolved due to the modification.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
For more information about the backlog parameter and Windows NT, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/113576/ )WinSocket applications reject connection requests with Reset frames
(http://support.microsoft.com/kb/127144/ )Windows NT WinSock Listen (Backlog) parameter limit
Article ID: 154628 - Last Review: September 24, 2008 - Revision: 5.0
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